JP2012516032A - Light source having light recycling device and corresponding light recycling device - Google Patents

Abstract

  The present invention relates to a light source 1 having a light emitting device 3 and a light recycling device 5, wherein the light recycling device 5 is located in an optical path 7 of the light emitting device 3. The light recycling device 5 is at least one light recycling member 9, and at least one light recycling member 9 for changing at least one physical property of light passing through the at least one light recycling member 9. , At least one heat conducting member 10, 11 capable of conducting heat generated in the light recycling member 9, wherein the heat conducting member 10, 11 includes the light recycling member 9 and at least one It is in thermal contact with the heat sink 12. The invention further relates to a corresponding recycling device 5.

Description

  The present invention relates to a light source having a light emitting device and a light recycling device, wherein the light recycling device is located in an optical path of the light emitting device.

  A light source having a light emitting device and a light recycling device is, for example, a light emitting diode (LED) that emits blue light and / or ultraviolet light, and generates white light by converting some wavelengths of the light into yellow light. It is known as a light source having a light recycling device that includes a phosphor plate in the light path of the LED. The brightness of the light source is limited by the thermal conductivity of the material used in the light recycling apparatus.

In the management of electronic circuit cooling, composite materials are widely used to increase the thermal conductivity. They can be used to manufacture heat sinks, can be included in packages, or can be included as layers in semiconductor devices, printed circuit boards, and the like.
In this field, light recycling materials must be suitable for recycling light even at the focus of high brightness light emitting devices.

  An object of the present invention is to provide a light source having a light emitting device and a light recycling device provided in an optical path of the light emitting device and having an increased heat adaptive range.

  To achieve this object, the light recycling device comprises at least one light recycling member for changing at least one physical property of light passing through the at least one light recycling member. A recycling member and at least one heat conducting member capable of conducting heat generated in the light recycling member, wherein the heat conducting member is thermally coupled to the light recycling member and the at least one heat sink. In contact.

Preferably, the light-emitting device is a high-intensity light-emitting device and / or a laser (laser) having a luminance of 1 · 10 ⁷ cd / m ² or more (10 meganits: 10 candela per square millimeters equal to 10 Mcd / m ² ). : Amplification of light by stimulated emission of radiation). The brightness (luminance) of the laser is at least 100 times higher (˜10 ⁹ cd / m ² vs. 10 ⁷ cd / m ² ) than the brightness achievable with conventional LEDs. The laser is preferably a solid state laser and / or a laser diode.

  In one embodiment of the invention, the change in the physical property of light is a wavelength conversion of the light and / or a change in the polarization state of the light. The light recycling member for changing the polarization state of the light is particularly a delay member or a depolarization member.

  According to another embodiment, the light recycling member is a phosphor plate and / or a phosphor thin film. The phosphor plate and / or phosphor thin film is a generally known wavelength conversion light recycling member. At the same time, the phosphor plate and / or phosphor thin film is a light recycling member that changes the polarization state of the light. The light or light beam emitted by the light emitting device is used to excite the phosphor plate and / or phosphor thin film. Said phosphor plate and / or phosphor thin film is preferably a cerium-doped yttrium aluminum garnet phosphor, or a ceramic phosphor, in particular a “Lumiramic” ceramic comprising an additional doping element (such as cerium or erbium) Made of phosphor.

While they can withstand high temperatures, recent experiments have shown that the conversion characteristics of phosphor ceramics are affected by temperature. High temperatures can be reached at the focus of the high-intensity light emitting device and / or laser. Power density reaches the number kW / cm ^2. This focal point is generally located in the phosphor plate or phosphor film of the light recycling apparatus. In this experiment, a decrease in light intensity emission due to the CECAS type ceramic was observed around 150 ° C., and a significant decrease in decay time was observed from 350 ° C. When the ceramic is heated, the efficiency is greatly reduced. This situation would occur with a 1 watt laser, for example.

  This dependence on temperature at the focal point reduces the ultimate efficiency of such a light source and can be a strong technical constraint. Recently, one of the main causes has been identified as the very low thermal conductivity of the phosphor material. The thermal conductivity of the ceramic has a very strong influence on the maximum temperature of the hot spot.

  In another embodiment of the present invention, the light emitting device is a light emitting device that emits blue light and / or ultraviolet light. The blue light and / or ultraviolet light emitted by the light emitting device preferably includes the phosphor plate or the phosphor thin film made of cerium-doped yttrium aluminum garnet phosphor and / or ceramic phosphor. Excited and used to create white light that exits the phosphor plate or phosphor film.

  In still another embodiment, the heat conducting member is a light polarizing member. The light polarizing member is based on an absorbing polarizer (such as a wire grid polarizer) and / or a beam splitting polarizer (such as a reflective polarizer, a birefringent polarizer and / or a thin film polarizer). In particular, the light polarizing member covers an entire surface of the light recycling member.

  Common applications where polarization is used are in LCD backlighting and LCD projection (LCD: liquid crystal display), and LC beam steering devices where the light beam emitted by the LED point source is operated in an LC cell (LC: liquid crystal). Is an option for. Linearly polarized light also affects reflections on the surface, which allows glare suppression and then affects the illuminated surrounding observation in saturation, observed contrast and visual acuity. As such, polarized light has advantages in both indoor and outdoor lighting. Because of this effect, polarized fluorescent emitters exist as commercial products with the required benefits in vision.

  According to a preferred embodiment of the present invention, the light polarizing member is a wire grid polarizer. Using advanced lithography techniques, very narrow pitch metal gratings that polarize visible light can be created.

  In another embodiment, the heat conducting member of the light recycling apparatus is a heat conducting layer disposed on a surface of the light recycling member and / or between two different parts of the light recycling member. It is formed. In particular, two heat conducting layers are disposed on the two surfaces of the light recycling member that are opposite to each other.

  According to a preferred embodiment, the thermally conductive layer is an at least partly reflective layer. In particular, one of the two heat conducting layers disposed on the two surfaces opposite to each other is a light polarizing member formed as a light polarizing layer, and the other layer is at least partially Reflective layer.

  According to another preferred embodiment, the heat conducting member is a diamond member and / or a sapphire member. In particular, at least one of the heat conducting member or the heat conducting member is a diamond layer and / or a sapphire layer. The diamond layer is preferably a diamond layer produced by CVD diamond growth (CVD: chemical vapor deposition). The high thermal conductivity of diamond allows thin film diamond coatings or layer diamond coatings to improve temperature controlled photonics and microelectronic devices.

  The thermally conductive layer formed as a diamond layer solves the thermal problem by increasing the local thermal conductivity of the material. It proposes the insertion of a layer material with an optimal thickness that would be sufficient to increase the equivalent overall thermal conductivity by a factor of 2 (up to 1400 W / mK).

This embodiment can be thermally enhanced to allow the light recycling device formed as a phosphor ceramic (Ce: YAG) to produce light with a power density of up to 16 kW / cm ^2. Suggest such a solution. In that case, the hottest spot reaches 310 ° C., which is appropriate to allow maximum light conversion in the material. The ceramic can be various types of ceramics, in particular polyceramics and / or single crystal ceramics, which are strongly scattering or transparent.

  Preferably, the light source further includes an optical element disposed between the light emitting device and the light recycling device. The optical element is located in an optical path of the light emitting device. In particular, the optical element is a light focusing element that focuses light emitted by the light emitting device within the light recycling member.

  In another embodiment, the light recycling apparatus further includes the heat sink. A light source including a light recycling device including the light recycling member, the heat conducting member, and the heat sink is very compact. In addition or in another embodiment, the light recycling apparatus further comprises a thermoelectric element and / or a Peltier element for cooling the heat conducting member, in particular the wires of the wire grid polarizer.

  According to another preferred embodiment, the light recycling member and the heat conducting member constitute a composite material of the light recycling device.

  The present invention further relates to an optical recycling apparatus for changing at least one physical property of light passing through the optical recycling apparatus. The light recycling apparatus includes at least one light recycling member and at least one heat conducting member capable of conducting heat generated in the light recycling member, and the heat conducting member is the light recycling member. It is in thermal contact with the member and the heat sink.

  The change in the physical property of the light is preferably a change in color and / or a change in polarization. More preferably, when the light recycling member is a phosphor plate or a phosphor thin film, and the light recycling member is located in an optical path of a light emitting device that emits blue light and / or ultraviolet light, the phosphor Formed as a phosphor plate or phosphor thin film, preferably made of cerium-doped yttrium aluminum garnet phosphor or ceramic phosphor to create white light exiting the plate or the phosphor thin film.

  In another embodiment, the heat conducting member is a light polarizing member. According to a preferred embodiment of the present invention, the light polarizing member is a wire grid polarizer.

  According to another preferred embodiment, the heat conducting member is a diamond member and / or a sapphire member.

  In particular, the light recycling apparatus further includes the heat sink.

  These and other aspects of the invention are described and elucidated with reference to the following examples.

1 is a side view of a light source for emitting polarized light having a light emitting device and a light recycling device according to a first embodiment of the present invention. FIG. 1B is a top view of a light source for emitting polarized light according to FIG. 1A. It is a side view of the light recycling apparatus of the light source by 2nd Example of this invention. It is a side view of the light recycling apparatus of the light source by 3rd Example of this invention.

  FIG. 1A shows a light source 1 formed as a light source 2 for emitting polarized light. The light source 1 includes a light emitting device 3, a light recycling device 5, and an optical element 6 formed as a laser (amplification of light by stimulated emission of radiation) 4 that emits light (laser light). The light recycling device 5 and the optical element 6 are disposed in the optical path 7 of the light emitting device 3, and the optical element 6 is a convex lens disposed between the light emitting device 3 and the light recycling device 5. The optical path 7 has a main axis 8.

  The light recycling apparatus 5 includes a light recycling member 9 for changing at least one physical property of light passing therethrough, and two heat conducting members 10 capable of conducting heat generated in the light recycling member 9. , 11 and a heat sink 12 formed as a frame surrounding the light recycling member 9. One of the heat conducting members 10 is located on the first surface of the light recycling member 9, and the first surface faces the optical element 6 and the light emitting device 3. The other heat conducting member 11 is located on the second surface of the light recycling member 9, and the second surface is located on the opposite side of the light recycling member 9 with respect to the first surface. Both heat conducting members 10, 11 are arranged perpendicular to the main axis 8 of the optical path 7.

  The heat conducting members 10 and 11 are formed as a light polarizing member 13, particularly a wire grid polarizer 14. The light recycling member 9 of the embodiment shown in FIGS. 1A and 1B is a phosphor thin film 15. The phosphor thin film 15 is a light recycling member 9 for wavelength conversion of light passing through it.

  The laser 4 emits blue light and / or ultraviolet light. The blue light and / or ultraviolet light emitted by the laser 4 excites the phosphor thin film 15 preferably made of cerium-doped yttrium aluminum garnet phosphor (YAG phosphor) or ceramic phosphor, Used to create white light (arrow 16) exiting thin film 15. A hot spot is created in the focal point 17 of the optical path 7. This hot spot is located in the light recycling member 9.

  An important feature of this embodiment of the present invention is that the phosphor thin film 15 (or (or) may be used to cool and dissipate hot spots created by blue light and / or ultraviolet light emitted by the light emitting device 3. Using a light polarizing member 13 (formed as a wire grid polarizer 14) placed on the surface of the phosphor plate. Depending on the configuration employed, when the back-reflected unconverted light returns to the light emitting device 3, a gain of polarization output can be obtained. In that case, according to the embodiment, recycling is intended to allow the reflected polarization to pass again through the light polarizing member 13 formed as a wire grid polarizer 14. In general, the polarization needs to be delayed in the retardation layer. In this embodiment, the role of the retardation layer is already fulfilled by the phosphor thin film 15 (or phosphor plate). In this case, the efficiency will be increased compared to a single pass of light with too much absorption (at best 50-55%).

  The wire grid polarizer 14 is made of metal, in particular aluminum or silver or gold, has a very high conductivity and the wire 19 of the wire grid polarizer 14 is in thermal contact with the larger heat sink 10. It allows heat to flow very efficiently towards the part 18. FIG. 1B shows a top view of a light source for emitting the polarized light of FIG. 1A.

  A 30 × 30 micron laser focus 17 is focused in the phosphor plate or phosphor film 15 and the laser 4 has a total power of 1 watt. Thanks to the wire grid polarizer 14 on the surface of the phosphor plate or phosphor thin film 15, the temperature of the light recycling device is reduced from 345 ° C. to 177 ° C. at the center of the laser beam on the second side (200 mW of heat Output dissipation). The second surface (the top surface in FIG. 1A) is the place where light absorption is strongest, so a decrease in the temperature of the surface will induce the highest gain in light conversion. The wire grid polarizer 14 moves the hottest points further down the YAG ceramic. The wire grid polarizer 14 is only arranged on the surface covering the laser spot (32 μm wide). The additional wire 19 will improve cooling a little.

  These results indicate that the addition of wire grid polarizer 14 will improve the temperature of the hot spot. In certain cases, it will make a difference between a fully efficient light conversion and a temperature limited conversion (due to a decrease in CECAS efficiency when the temperature reaches about 350 ° C.). .

  The wire 19 of the wire grid polarizer 14 outside the optical path 7 has a different thickness, in particular thicker than in the region in the optical path (not shown) and is joined together with welding tape and / or other fasteners. It is important to realize what is done. This makes it easy to manufacture the light recycling apparatus 5.

  FIG. 2 is a side view of the light recycling apparatus 5 for the light source 1 according to the second embodiment of the present invention. The heat conducting member 10 is formed as a heat conducting layer 20 disposed between two different portions 21, 22 of the light recycling member 9. The heat conductive layer 20 is formed as a diamond member 23, in particular, a diamond layer 24.

The method of manufacturing the light recycling apparatus 5 is as follows:
Applying a diamond layer 24 to the surface of the first part 21 of the light recycling member 9, in particular the first part 21 formed as a phosphor plate 25;
Applying a second portion 22, in particular a phosphor thin film 15, on the surface of the diamond layer 24;
Cutting the composite device of the first part 21, the diamond layer 24 and the second part 22 into a final shape as used in the light recycling member 9;
Assembling the composite device and the heat sink 12;

  In particular, the diamond layer 24 is deposited by CVD on a phosphor plate 25, in particular a YAG ceramic phosphor plate. Next, the phosphor thin film 15 is deposited on the diamond layer 24. This can be done at a thickness of 10 to 50 micrometers. The composite device is then cut using a cutting tool and inserted into the copper heat sink 12.

  The embodiment solves the thermal problem by increasing the local thermal conductivity of the light recycled material. It proposes the insertion of a diamond layer 24 with an optimal thickness that would be sufficient to double the equivalent overall thermal conductivity.

In the specific case of a 100 × 100 micron and 150 micron thick ceramic phosphor plate 25 with a power density of 16 kW / cm ² (in the hottest spot) and a 30 micron spot size laser beam, 10 micron A diamond layer 24 with a thickness of 100 × 100 microns is inserted (so that the layer is in contact with the heat sink 12). This diamond layer 24 is located in the material 20 microns away from the top surface, as shown in FIG.

  Consider a bulk phosphor plate (eg Ce: YAG) with a thermal conductivity of 3 W / mK, which can vary in size. This phosphor material 15, 25 of the plate 23 is surrounded by a heat sink 12 made in particular of copper (except at the top) to allow the laser beams to interact and extract the light.

  In a different configuration (not shown), six clusters of 10 × 10 micron diamond are uniformly arranged in the phosphor material. In this way, a composite material is realized. Only two of these clusters touch the wall of the heat sink 12 (which is important for cooling). In that case, the improvement is slight. However, in this way it is not actually possible to model an actual composite material. Especially in the range of nanometer-sized particles, there is a strong dependence on the size and shape of the particles. The thermal conductivity of the composite material will also depend on the volume fraction. It can be assumed that comparable sizes can be compared to existing composite materials (such as diamond-copper). In these types of composite materials, the thermal conductivity can be almost doubled (up to 742 W / mK). In this case, however, a very high volume ratio of diamond is required. The ratio is from 50% to 90%. This may be too high for wavelength conversion. This is because a phosphor material is used to generate white light, which means that the phosphor must remain in the same state as much as possible. Too many other particles can reduce photonic properties.

  FIG. 3 shows a side view of the light recycling apparatus 5 of the light source 1 according to the third embodiment of the present invention. A diamond layer 24 is deposited on a phosphor plate 25 having a thickness of 100 to 150 microns. A thin adhesive layer 26 on the diamond layer 24 connects another phosphor plate 27 (thick enough to be mechanically robust). Thereafter, the other side of the other phosphor plate 27 is polished to obtain a phosphor thin film 15 (YAG layer) having a thickness of 20 micrometers.

  The method is different from the above method in that the second portion 22 is attached by the adhesive bonding of the second portion and the manufacture of the phosphor thin film 15 by the subsequent polishing.

  In another example, the diamond layer 23 is not sandwiched and is deposited on the top surface of the ceramic (not shown). In order to have sufficient heat transfer, the surface contact between the diamond layer 24 and the heat sink 12 should be increased. This can be achieved by performing a ceramic CVD process. In that case, in order to optimize the surface contact, the individual pieces of ceramic can be cut and inserted into an appropriately sized copper mass.

  In short, a technique for dealing with high-temperature hot spots of laser light in the phosphor materials 15 and 25 can be applied. The proposal is to use a diamond layer 24. This is because the manufacturing process is similar and the thermal conductivity improvement is much higher, especially high enough to deserve it in the case of diamond. In this configuration, the high intensity laser 4 can be focused within the phosphor plate and white light can be generated in a very small spot. This solution is sufficient on its own and will not require any additional active cooling. This is the safest way in which high intensity white light with micrometer spots can be created in phosphor materials. This will expand the application area of white light.

  The light recycling apparatus 5 (FIGS. 2 and 3) according to the second and third embodiments of the present invention can be used for the reflective assembly and the light transmissive assembly of the light source 1. Within the transmissive assembly, the heat sink 12 has a channel that allows the laser beam to pass light through the heat sink 12 and / or in other examples has a transparent heat sink 12 such as a sapphire heat sink.

  While the invention is illustrated in the drawings and has been described in detail in the foregoing description, such illustration and description are to be considered illustrative and exemplary and limited Should not be considered. The invention is not limited to the disclosed embodiments.

  Those skilled in the art in practicing the claimed invention may understand and achieve other variations to the disclosed embodiments from a study of the drawings, the specification, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the singular form does not exclude the presence of a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims (14)

  A light source having a light emitting device and a light recycling device, wherein the light recycling device is a light source located in an optical path of the light emitting device, and the light recycling device is at least one light recycling member, At least one light recycling member for changing at least one physical property of light passing through the at least one light recycling member, and at least one heat capable of conducting heat generated in the light recycling member A light source, wherein the heat conducting member is in thermal contact with the light recycling member and at least one heat sink. The light source according to claim 1, wherein the light emitting device is a high brightness light emitting device and / or a laser having a luminance of 1 · 10 ⁷ cd / m ² or more.   The light source according to claim 1, wherein the change in the physical property of light is a wavelength conversion of the light and / or a change in a polarization state of the light.   The light source according to claim 1, wherein the light recycling member is a phosphor plate and / or a phosphor thin film.   The light source according to claim 1, wherein the light emitting device is a light emitting device that emits blue light and / or ultraviolet light.   The light source according to claim 1, wherein the heat conducting member is a light polarizing member.   The light source according to claim 6, wherein the light polarizing member is a wire grid polarizer. The heat conducting member of the light recycling apparatus is
The light source according to claim 1, wherein the light source is formed as a heat conductive layer disposed on a surface of the light recycling member and / or between two different portions of the light recycling member.   9. A light source according to claim 8, wherein the thermally conductive layer is an at least partially reflective layer.   The light source according to claim 1, wherein the heat conducting member is a diamond member and / or a sapphire member.   The light source according to claim 1, wherein the light recycling apparatus further includes the heat sink.   The light source according to claim 1, further comprising an optical element disposed between the light emitting device and the light recycling device.   The light source according to claim 1, wherein the light recycling member and the heat conducting member constitute a composite material of the light recycling apparatus.   An optical recycling device for changing at least one physical property of light passing through the optical recycling device, the optical recycling device comprising at least one optical recycling member and the optical recycling An optical recycling apparatus comprising: at least one heat conducting member capable of conducting heat generated in the member, wherein the heat conducting member is in thermal contact with the light recycling member and the heat sink.

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